The majority of the 100 extra officers will be of constable rank, and the unit will lose Duthie, who will become head of homicide next month, and one superintendent.

Duthie said officers would retain their specialisms in the types of crime they investigate. "We've made a conscious decision that this is a high-risk area, we need to have dedicated officers investigating dedicated types of crime.

"There will be separate rape teams and separate child abuse teams."

High-profile investigations such as Operation Yewtree, the inquiry triggered by abuse allegations against Jimmy Savile, will come under the new command.

Questions have been raised over whether the new unit should abandon the name Sapphire because of trouble in the past.

In February in its latest report on the Southwark rape unit the police watchdog found that women had been pressured to drop rape allegations.

The Independent Police Complaints Commission (IPCC) said that these included a woman who had made a claim against Jean Say, who later went on to murder his two children.

The watchdog also found that Scotland Yard had failed to hold gross misconduct proceedings against three officers involved in the case of repeat sex offender Kirk Reid. Two of the officers had in fact been promoted.

Reid was found guilty of attacks on 25 women over a 12-year period in the Balham, Clapham and Tooting areas of south-west London.

It emerged during his trial that police did not arrest him until four years after he was first named as a suspect and a separate IPCC inquiry was carried out into apparent blunders and failings.

The Met said the officers had been dealt with as appropriate and that changes had been made to the way the force dealt with sex crime.

Duthie said: "We've certainly had our ups and downs and unfortunately it seems that the downs get reported.

"We've spoken to our partners about whether we will change the Sapphire name and some are saying get rid of it, some are saying a lot of people know what Sapphire does and if you lose that you will lose some victims' ability to contact police."

A Metropolitan police spokeswoman said that the name would not necessarily fit because it is associated only with rape investigations.